New Mechanism May Improve Hearing Aids

Diagram of the structure of the human ear. Source: MIT.

Scientists at the Massachusetts Institute of Technology in Cambridge, Massachusetts have been researching how the human ear distinguishes between sounds with subtle differences. They have identified a particular mutation affecting the tectorial membrane inside the inner ear which interferes with the way sounds are sorted during the hearing process. Researchers hope that further study of this mechanism may lead to new hearing aids and other assistive devices that are much more effective than the models currently on the market.

Scientists have long known that hair cells along the basilar membrane inside the cochlea translate sound waves into electrical impulses that are then sent to the brain for further processing. Different frequencies of sound waves are captured by the hair cells at different points along the membrane which helps the brain identify the frequency and sort complex sounds into recognizable patterns.

Several years ago MIT researchers Dennis Freeman and Roozbeh Ghaffari identified that the tectorial membrane – a small string of gel material less than an inch long and thinner than a single strand of human hair – also plays a role in this process. They discovered that sound waves that move up and down travel along the basilar membrane while those that move side to side travel along the tectorial membrane.

Freeman, Ghaffari, and several other collaborators recently discovered that sound waves did not travel as fast or as far along the tectorial membrane in mice missing the TectB gene (which encodes one of three proteins that form the tectorial membrane) as compared to mice with that gene intact. This leads to fewer hair cells being stimulated, making it more difficult to distinguish between similar sounds.

The researchers hope to use this discovery to develop a new generation of hearing aides capable of tuning into specific ranges of frequencies correlating to the human voice. Hearing aides today are not able to focus on specific sounds but rather amplify all of the sounds input into them, both signal and noise.

Janice Karin has a B.A in physics from the University of Chicago and a
M.S. in physics from the University of Pennsylvania. In addition to
extensive experience as a technical writer focused on development
tools, databases, and APIs, Janice has worked as a freelance reporter,
editor, and reviewer with contributions to a variety of technology
websites. One of her primary focuses has been on PDAs and mobile
devices, but she is interested in many other areas of science and
technology.